System and method for frequency re-use in a sectorized cell pattern in a wireless communication system

ABSTRACT

The present invention relates to a system and method for frequency re-use in a wireless communication system. More particularly, the inventive system and method provides for maximum coverage of a service area with a pattern of cells each having a sectorized hub antenna pattern where only a limited number of communication channels are available.

RELATED APPLICATIONS

The present application is related to co-pending, commonly assigned U.S.patent application Ser. No. 09/434,707, entitled “SYSTEM AND METHOD FORBROADBAND MILLIMETER WAVE DATA COMMUNICATION,” co-pending, commonlyassigned U.S. patent application Ser. No. 09/604,437, entitled“MAXIMIZING EFFICIENCY IN A MULTI-CARRIER TIME DIVISION DUPLEX SYSTEMEMPLOYING DYNAMIC ASYMETRY,” and co-pending, commonly assigned U.S.patent application Ser. No. 09/607,456, entitled “FREQUENCY REUSE FORTDD,” which are incorporated herein by reference. The presentapplication is also being filed simultaneously with a commonly assignedU.S. patent application entitled “SYSTEM AND METHOD FOR INBAND SIGNALINGFOR SECTOR SYNCHRONIZATION IN A WIRELESS COMMUNICATION SYSTEM”.

BACKGROUND OF THE INVENTION

The present invention relates to communication systems and methods andmore particularly to a system and method for optimizing the bandwidth ofa point to multipoint wireless system by synchronizing transmit andreceive modes.

Wireless radio links have increasingly become important to provide datacommunication links for a variety of applications. For example, InternetService Providers have begun to utilize wireless radio links withinurban settings to avoid the installation expense of traditional wiredconnections or optical fiber. It may be advantageous to utilize wirelessradio link systems to provide service to a plurality of users in a pointto multipoint architecture. Point to multipoint systems typicallyconsist of a plurality of hub units servicing a plurality of sub units(sometimes referred to as remote units, nodes, or subscriber units). Thesubs are typically associated with individual nodes on the system. Forexample, an individual sub unit may be connected to LAN to allow PC's onthe LAN to bridge to other networks via the point to multipoint system.Each sub unit communicates via a wireless channel with a particular hubunit. In a point to multipoint system, the hub unit may controlcommunication between a portion of the plurality of sub units associatedwith a particular coverage area. The hub units schedule transmit andreceive bursts to and from sub units. The hub units may distribute datapackets received from a particular sub unit to another sub unit withinthe same coverage area via such frames, to a traditional wired networkbackbone, or to another hub unit.

A point to multipoint system, such as disclosed in the above referencedand commonly assigned patent application entitled “FREQUENCY REUSE FORTDD,” contains a plurality of adjacently located hub units providing anaggregate coverage area. Additionally, these hubs may have theirindividual coverage areas divided into particular sectors—such as 30 or90 degree sectors. Additionally, the hubs may utilize frequency divisionor other techniques to provide a plurality of communication channels.

Channel reuse techniques have developed to allow reuse of channelswithin a network without introducing unacceptable levels ofinterference. The purpose of these channel reuse techniques is maximizechannel availability while avoiding co-channel interference betweenneighboring hubs. Clearly, these channel reuse techniques are valuabletools to increasing the bandwidth of point to multipoint systems.However, according to the present invention it has been realized thatpoint to multipoint systems contain architectural characteristics thatmay be exploited to allow optimization of channel availability greaterthan that available with traditional channel reuse techniques whileavoiding co-channel interference.

For example, data traffic over a point to multipoint system may bebursty, rather than at a fixed or continuous data rate. Specifically, anInternet browser application executed on a sub unit would typicallyrequire significant down link bandwidth while downloading HTML code froma website, but would require little or no bandwidth while a user readsthe display associated with the HTML code. Additionally, the bandwidthrequirements of many applications such as browsers may be asymmetric.Specifically, Internet browsers often download a large amount of data,but upload proportionally very little. Accordingly, point to multipointsystems may implement dynamic bandwidth allocation (DBA) techniques tomaximize the data throughput associated with asymmetric, bursty traffic.

Accordingly, it is an object of the present invention to provide asystem and method to maximize the bandwidth of point to multipointsystems in accordance with the unique characteristics of point tomultipoint systems as between particular portions of the network.

It is an additional object of the present invention to provide a systemand method for synchronized dynamic allocation of bandwidth.

It is an additional object of the present invention to provide a systemand method for synchronization of receive and transmit modes of sectorsor other portions of an associated group of hub units to maximize thebandwidth of point to multipoint systems.

It is an additional object of the present invention to provide a systemand method for sector to sector telemetry in point to multipointsystems.

It is an additional object of the present invention to provide anefficient communication channel for use with the invention systems andmethods that allows synchronization of neighboring hubs while permittingrapid dynamic allocation of bandwidth in individual hubs.

It is still an additional object of the present invention to provide apattern of frequency re-use in a wireless communication system.

It is another object of the present invention to provide a repeatablepattern of frequency re-use in a wireless communication system comprisedof sixteen cells in a four-by-four grid using two polarizations percommunication frequency.

It is yet another object of the present invention to provide arepeatable pattern of frequency re-use in a wireless communicationsystem comprised of sixteen cells grouped in four sub-clusters of fourcells in which facing sectors in the pattern are synchronized.

It is a further object of the present invention to provide a method ofreducing co-channel and/or adjacent channel interference by a pattern offrequency re-use.

These and other objects, features and technical advantages are achievedby a system and method which operate in a point to multipoint systemcomprising a plurality of hubs and a plurality of subs distributedwithin coverage areas associated with the hubs. The point to multipointsystem preferably divides its communication bandwidth into channelsutilizing spectrum division techniques, such as frequency division, timedivision, or orthogonal code division. Also, the hubs communicate to thesubs within their coverage areas via sector antennae. By utilizingspectrum division and sector antennas, preferred embodiments of thepoint to multipoint system coordinate channel allocation via a channelreuse plan. Additionally, preferred embodiments divide individualchannels into transmit and receive modes via a Time Duplex Division(TDD) scheme via the same channel. In this TDD scheme, a hub transmitsinformation to subs in the transmit mode and receives information fromsubs in the receive mode. Moreover, the hubs of the point to multipointsystem preferably may dynamically allocate bandwidth between thetransmit and receive modes to achieve asymmetric communication modes.Also, the preferred embodiment subs utilizing the present inventioncomprise directional antenna.

Co-channel interference such as in adjacent sectors of neighboring hubsis a significant concern. Specifically, hub to hub exposure isproblematic, since hub antennas are typically directed toward other hubsof the network in order to provide composite coverage of a service area.For example, preferred embodiment hubs may utilize sector antennascovering between 30 to 90 degrees in azimuth, which are oriented to facesimilar sector antennas at neighboring hubs. Sub unit exposure is not asa significant issue for the preferred embodiments point to multipointsystems, because sub units of these point to multipoint systems utilizehighly directional antenna. Accordingly, the subs units may not beexposed to significant co-channel interference from other sub units orother hub units.

Channel reuse plans may be utilized to mitigate hub to hub co-channelinterference. For example, by carefully assigning channels for use bythe hubs of a network, reuse performance of approximately 1 may beachieved. Moreover, through advanced channel planning techniques, suchas shown and described in the above referenced patent application,entitled “FREQUENCY REUSE FOR TDD”, and as described below, higherchannel reuse performance may be achieved.

Nonetheless, a method or system optimization that would permit greaterchannel reuse would allow greater bandwidth for the system as a whole.The present invention achieves this goal in one embodiment bysynchronizing transmit and receive modes of hubs. One embodiment of thepresent invention synchronizes dynamic bandwidth allocation of facingsectors of a cluster of geographically adjacent hubs, while allowingother sectors of these hubs to independently allocate bandwidth throughfrequency reuse and facing sector synchronization. The hubs are adjacentin the sense that the hubs are the nearest neighbor hubs in a particulardirection. In this embodiment, guard time between transmit and receivemodes is minimized by preferably selecting a guard time to accommodatethe synchronization distance of just over two hub coverage radii. Forexample, where a maximum reuse is 6R, a reuse schedule of 9, with 30degree sectors, 4.5 km cells, the guard time is approximately 100 μs orapproximately 5% of the embodiment's channel capacity to accommodatepropagation from a maximum distance in the reuse cluster. However, asthe present invention synchronizes facing sectors of adjacent hubs, thesynchronization distance is greatly reduced. Accordingly, in thisembodiment, the guard time only occupies 0.5% of the channel capacity.Moreover, the computation requirements of the system are significantlyreduced in this preferred embodiment, as a much smaller portion of thenetwork is synchronized with respect to any particular synchronizationdetermination. Also, the facing sector synchronization simplifies theimplementation of synchronization telemetry.

In another embodiment of the present invention, a pattern of frequencyreuse is described where a repeatable pattern of cells is employed toallow for re-use of a number of frequency assignments where there aretwo polarization modes available per frequency. Such a pattern offrequency re-use is especially useful when the number of frequencyassignments, or communication channels, available for operation of acommunication system is limited. In order to provide sufficient coveragefor a particular operating area, a pattern of cells that re-use theavailable frequencies must be provided in order to avoid dead spots orto avoid interference between adjacent channels on the frequencyspectrum used in the same area, known in the art as “adjacent channelinterference” or interference between two cells using the same frequencywith the same polarization in adjacent areas, known in the art as“co-channel interference”.

Idealizing the shape of the cells in the pattern as circular and furtheridealizing each cell as having a similar radius, the shape of arepeatable pattern of such cells can be viewed as an overlay on a flatsurface. Obviously, such idealizations such as a flat surface andsubstantially identical cells spaced at uniform distances rarely occurin the real world. However, it is to be understood that the presentinventive system and method is not limited to such idealizations butrather is applicable to real world situations where the overallfrequency re-use pattern can be used while taking into account minorvariations to allow for obstructions, terrain features, dissimilar cellsizes, irregular spacing of cells, etc. While the disclosure of theinvention below will discuss an idealized repeatable pattern composed ofidealized cells, etc., such idealizations should not be construed aslimitations of the invention.

For cells of substantially the same size and circular in shape, onearrangement of those cells in a multi-cell pattern may be seen as asquare grid where the edge of two cells that are adjacent in the samerank or the same file are tangent at one point. In such an arrangement,cells that are diagonally adjacent are not tangent. In anothermulti-cell arrangement, a cell in the pattern is tangent to each of sixadjacent cells. Such a pattern would appear as a honeycomb shape if thecells are idealized to be hexagonal in shape.

The inventors have determined empirically that for cells with 90°sectors, a minimum of eight frequency assignments and two polarizationsare required for efficient frequency re-use for broadband wirelessaccess systems. This is a reasonable requirement offrequency/polarization assignments for 90° sectorized cells in a timedivision duplex (“TDD”) system considering the size of a typical licenseallocation of frequencies on a worldwide basis. For example, in Europe,the anticipated license allocation is 2×112 MHz or 224 MHz for the 28GHz band and approximately 500 MHz for the 42 GHz band. Most of theNorth American broadband wireless access operators have allocations inexcess of 200 MHz. An emerging popular channel size is 28 MHz in Europeand 25 MHz in North America. These channel sizes coupled with theanticipated license allocation of frequencies allows for eight or moreavailable frequency channels.

While 90° sectors have some disadvantages over smaller sector sizes,such as 60°, 45°, and 30° sectors, 90° sector size is the baseline forplanning for almost all broadband wireless access operators andstandards groups. For example, RF performance is somewhat compromisedfor wide sectors relative to narrow sectors. Cell diameter is reducedthereby requiring a greater number of hubs/cells to cover a given area.Wider sectors also give rise to a greater possibility of co-channel andadjacent channel interference.

Despite the operational drawbacks of 90° sectors, there are significanteconomical advantages to 90° sector plans. One advantage is the lowercost of outdoor gear. With 90° sectors, fewer sectors and hence fewerradios, antennas, and associated equipment, both primary and redundant,are required when compared with smaller-sized sectors. Additionally, asignificant cost to operators are roof rights. Landlords tend to chargefor the right to place equipment of the roof of their building based onthe number of antennas so 90° sectors translates into lower cost forroof rights. Also, wider sectors provide greater RF coverage which is animportant benefit in the early deployment of a system.

The foregoing has outlined rather broadly the features and technicaladvantages of the present invention in order that the detaileddescription of the invention that follows may be better understood.Additional features and advantages of the invention will be describedhereinafter which form the subject of the claims of the invention. Itshould be appreciated by those skilled in the art that the conceptionand specific embodiment disclosed may be readily utilized as a basis formodifying or designing other structures for carrying out the samepurposes of the present invention. It should also be realized by thoseskilled in the art that such equivalent constructions do not depart fromthe spirit and scope of the invention as set forth in the appendedclaims. The novel features which are believed to be characteristic ofthe invention, both as to its organization and method of operation,together with further objects and advantages will be better understoodfrom the following description when considered in connection with theaccompanying figures. It is to be expressly understood, however, thateach of the figures is provided for the purpose of illustration anddescription only and is not intended as a definition of the limits ofthe present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawing, in which:

FIG. 1 depicts an illustrative example of a point to multipoint systemarranged in a cluster architecture.

FIG. 2A depicts an illustrative sector configuration for the point tomultipoint system set forth in FIG. 1.

FIG. 2B illustrates a sectorized antenna arrangement for a hub for oneof the cells in FIG. 2A.

FIG. 3 illustrates particular sectors and the propagation oftransmissions from hubs to a plurality of subs within the particularsectors.

FIGS. 4A to 4D each illustrate a timing diagram for a series of RX andTX frames associated with opposing sectors of adjacent hubs.

FIG. 5 illustrates an exemplary power density spectrum for a QAM carriersignal and an associated Adaptation carrier.

FIG. 6A illustrates a set of eight frequency channels with twopolarizations per frequency channel for use in a frequency re-usepattern.

FIG. 6B illustrates eight unique cell types using the set of eightfrequency channels with two polarizations per frequency channelillustrated in FIG. 6A.

FIG. 7 illustrates a repeatable pattern of sixteen cells in afour-by-four rectilinear grid where each cell is divided into four 90°sectors where opposing sectors operate on the same frequency channelwith the same polarization.

FIG. 8 illustrates one group of four cells from the repeatable patternof sixteen cells in FIG. 7.

FIG. 9 illustrates a repeatable pattern of sixteen cells in afour-by-four grid forming a parallelogram where each cell is dividedinto four 90° sectors where opposing sectors operate on the samefrequency channel with the same polarization.

FIG. 10 illustrates a repeatable pattern of FIG. 7 where facing sectorsoperate on the same frequency channel and polarization to allow fortransmit and receive synchronization between hub antennas of facingsectors.

FIG. 11A illustrates the set of eight frequency channels with twopolarizations per frequency channel shown in FIG. 6A indicating thosefrequency channels and polarizations used in the pattern in FIG. 10 andthose frequency channels and polarizations not used in the pattern ofFIG. 10 that are held in reserve.

FIG. 11B illustrates eight unique cell types using the set of fourfrequency channels with two polarizations per frequency channelillustrated in FIG. 11A as being used in the frequency re-use pattern ofFIG. 10.

FIG. 12 illustrates one group of four cells from the repeatable patternof sixteen cells in FIG. 10.

FIG. 13 illustrates the repeatable pattern FIG. 10 with an overlay ofadditional frequency channel sectors to accommodate an increase in thecapacity demands of the users of the system.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary point to multipoint system utilizing thepresent invention. The system is preferably deployed in a clusterconfiguration. The illustrative cluster consists of a plurality of hubs(105, 106, 107, 108), although clusters in numbers different than theillustrated configuration may be employed according to the presentinvention. It shall be appreciated that communication networks utilizingthe present invention may include additional clusters, either remotelylocated or adjacently located, with the clusters utilizing the presentinvention.

Hubs 105, 106, 107, and 108 provide coverage to cells 101, 102, 103, and104. A plurality of subs (109-119) are deployed in cells 101, 102, 103,and 104, respectively. In addition, processor systems (120-131) arerespectively associated with individual sub units. It shall beappreciated that sub units of a point to multipoint system may bealternatively associated with a LAN network of processors system.Alternatively, the sub units of point to multipoint system may beconnected to an intermediate network. For example, a sub unit may beconnected to an intermediate ATM switch. It shall further be appreciatedthat a system employing the present invention may contain an arbitrarilylarge number of hubs, cells, and sub units. For simplicity of describingthe present invention, the exemplary embodiment has been described interms of four cells.

FIG. 2A illustrates an exemplary sector configuration of the point tomultipoint system set forth in FIG. 1. As previously noted, the systemis divided into coverage areas associated with cells 101, 102, 103, and104. Moreover, cells 101, 102, 103, 104, of the illustrated embodimentare sectorized into 90 degree sectors (101A-101D, 102A-102D, 103A-103D,and 104A-104D), although other sector sizes may be synchronizedaccording to the present invention. Hubs 105, 106, 107, and 108 transmitand receive signals to/from the sectors via sector antennas, such asillustrated in FIG. 2B for the hub 105. The sector antennas 202A through202D may utilize a discrete antenna element for each sector.Alternatively, the sector antennas may utilize a plurality of narrowbeam antenna elements to synthesize sector coverage. In thisconfiguration, energy from RF signals transmitted from a sector antennaassociated with any of sectors 101D, 102C, 103B, and 104A may bedetected in the other sector antennas of this group.

The spectrum allocated to the point to multipoint system as a whole ispreferably subdivided into channels. Numerous methods of channeldivision may be utilized with the present invention, such as timedivision, frequency division channels, frequency hopping channels, andorthogonal code channels. The channels are divided into discrete sets.Additionally, the sets of channels are allocated among the sectors ofthe point to multipoint system in accordance with a reuse schedule. Inthis exemplary system, RF signals 302-307 are being transmitted upon thesame channel for the purpose of illustrating the present invention. Itshall be appreciated that other signaling may occur on other channelsconcurrently with the exemplary transmit and receive signals.

According to a preferred embodiment, at least adjacent sectors of aparticular cell are provided different channel sets according to thechannel reuse plan. For example, the channels assigned for use bysectors 104B and 104C are different from the channels assigned for useby sector 104A. However, depending upon the front and back isolation ofthe sector antenna, side lobe characteristics, and the like, channelsets may be reused in a cell, such as within sector 104B and 104C and/or104A and 104D.

FIG. 3 illustrates a series of RF transmit signals (301-306) broadcastfrom hubs 105 and 106, respectively. Hub 105 transmits a series of RFtime burst or time slot signals (302, 303, and 304) with the signalspropagating in direction 301 within sector 101D. Since hub 105 utilizesa sector antenna, the energy associated with RF signals 302, 303, and304 propagates through out sector 101D. RF signal 302 comprisesinformation for sub 109. RF signal 303 comprises information for sub110. RF signal 304 comprises information for sub 111. Similarly, hub 108transmits a series of RF time burst or time slot signals (305, 306, and307) with the signals propagating in direction 308 within sector 104A.Since hub 104 utilizes a sector antenna, the energy associated with RFsignals 305, 306, and 307 propagates through out sector 104A. RF signal305 may comprise information for sub 117. RF signal 306 may compriseinformation for sub 118. RF signal 307 may comprise information for sub119.

Eventually, RF signals 302, 303, and 304 will propagate beyond theconfines of cell 104 into cells 101, 102, and 103. Accordingly, RFsignals 302, 303, and 304 could cause co-channel interference in cells101, 102, and 103. In the preferred embodiment point to multipointsystem, the sub units utilize highly directional antennas directedtoward an associated hub and therefore generally away from the remaininghubs of a cluster. Accordingly, the subs generally will not experienceco-channel interference from RF signals 302, 303, and 304.

However, hubs 105, 106, and 107 will experience co-channel interferenceif the hubs are in receive mode with respect to the particular channelsassociated with RF signals 302, 303, and 304 when the RF signals arriveat the particular hub. According to a preferred embodiment, hub 108utilizes the same set of channels for sector 104A as hub 105 utilizesfor sector 101D, hub 106 uses for sector 102 c, and as hub 107 uses forsector 103 b. Accordingly, RF signals 302, 303, and 304 could causeco-channel interference depending upon their arrival time at hubs 106,107, and 108. It shall be appreciated that RF signals 302, 303, and 304will have negligible effect if RF signals 302, 303, 304 arrive when hubs106, 107, and 108 are in transmit mode. Similarly, RF signals 305, 306,and 307 may cause co-channel interference in hubs 105, 106, and 107, ifthe hubs are in receive mode with respect to the channels associatedwith the signals upon their arrival.

Additionally, the subs in sectors 101D and 104A broadcast RF signals309-314. As previously noted, the sub units of the preferred embodimentof this system utilize highly directional antennas. The architecture ofthe system is such that the highly directional antennas focus theradiated RF energy within a very narrow beam centered upon therespective hubs. Accordingly, it is unlikely that the subs could couplewith another antenna in the system to cause co-channel interference. Itshall be appreciated that this exemplary system contemplates that RFsignals 302-307 and RF signals 309-314 are being transmitted via thesame frequency channel. Accordingly, the exemplary system illustratingthe present invention controls the timing of RF signal transmissions inTDMA burst periods.

The preferred embodiment of the present invention and methodsynchronizes particular transmissions within a point to multipointsystem to prevent hub transmission from causing co-channel interference.Of course, reception windows may also be synchronized in addition to orin the alternative to transmission window synchronization in accordancewith the present invention. Depending upon the amount of isolationbetween channels, it may be possible to independently synchronizeindividual channels in adjacent sectors. By synchronizing individualchannels, an adaptive time division duplex scheme may maximizethroughput on a per channel basis. However, this approach requiresgreater processing capacity, and hence greater equipment costs andcomplexity, to calculate optimal receive and transmit asymmetries.Accordingly, the preferred embodiment synchronizes transmission andreception for all channels utilized within adjacent sectors. In thismanner, the present system and method allows greater performance of theasymmetric time division duplex algorithms while maintaining costs andcomplexity at preferred levels.

FIGS. 4A through 4D set forth exemplary timing diagrams for transmit andreceive frames for sectors 101D, 102C, 103B, and 104A of hubs 105, 106,107, and 108. Each hub is preferably synchronized to begin its transmitmode at time to. Hub 105 transmits TX bursts 401-403, comprisinginformation for subs 109-111, respectively. Hub 106 transmits TX burst404 comprising information for sub 114. Hub 107 transmits bursts 405 and406, comprising information for subs 115 and 116, respectively. Hub 108transmits bursts 407-409, comprising information for subs 117-119,respectively. Also, each hub is preferably synchronized to end itstransmit mode at time t₆.

Additionally, hubs 105-108 are further synchronized such that hubs105-108 do not transmit from time t₆ to time t₇. Also, hubs 105-108 donot receive bursts from subs from time t₆ to time t₇. During thisperiod, the delay in transmission and reception creates guard 316. Theduration of guard 316 is preferably selected so that the RF signalsassociated with the respective bursts will propagate beyond any hub thatmay experience co-channel interference before the hub will enter receivemode. Adjacent sector synchronization causes the synchronizationdistance for this embodiment to be slightly more than two hub radii (thedistance between hubs 105 and 108). Adjacent sector synchronization withproper reuse planning is sufficient, because non-synchronized sectorsutilizing the channels will be sufficiently separately spatially orfacing different directions to avoid co-channel interference.

An exemplary discussion of such frequency reuse planning is contained inthe above reference patent application, entitled “FREQUENCY REUSE FORTDD.” In an environment utilizing frequency use, channels may beassigned to hubs and their respective sectors by storing assignedchannels in non-volatile memory at a hub which is utilized to physicallyconfigure the hub during a configuration start-up operation.Alternatively, channels may be assigned upon a dynamic basis inaccordance with dynamic channel assignment algorithms. In this case, achannel controller may implement a particular dynamic assignmentalgorithm and periodically communicate assigned channels to the hubs foruse in the respective sectors.

After time t₇, hubs 105-108 are synchronized to enter the receive mode.At this point, hubs 105-108 may receive transmissions from theirrespective subs without detecting RF signals transmitted from the otherhub. During the receive mode, hub 105 receives RX bursts 410-412 fromsubs 109-111, respectively. Hub 106 receives RX bursts 413 from sub 114.Likewise, hub 107 receives RX bursts 414 and 415 from subs 115 and 116,respectively. Hub 108 receives RX bursts 416-418 from subs 117-119,respectively. Hubs 105-108 are preferably synchronized to end theirreceive modes at time t₁₃.

Additionally, this embodiment provides other advantages. First, adjacenthubs are capable of direct communication and therefore may coordinateframe timing and/or channel allocation without the use of separatetelemetry lines. Secondly, the telemetry bandwidth necessary tocoordinate channel allocation in a synchronous manner is significantlyreduced in the adjacent hub configuration. Moreover, adjacent sectorsynchronization requires much less computation capacity thancluster-wide synchronization.

It shall be appreciated that the present invention allows greater systemutilization and performance through other considerations in addition togreater channel reuse. By synchronizing adjacent sectors or adjacentantenna beams, the present invention does not place any other arbitraryrestrictions upon the transmit and receive asymmetries associated withother sectors or antenna beams. For example, it is possible that subunits in adjacent sectors aggregately require significant transmitbandwidth but little receive bandwidth at a particular moment in time.Concurrently, it is possible that sub-units of non-adjacent sectors mayaggregately require inverse bandwidth requirements. If the entire groupof sectors were synchronized, a portion of the bandwidth would be wastedin both the adjacent and non-adjacent sectors. Accordingly, the presentinvention operates the transmit and receive asymmetries of adjacentsectors independently of other asymmetries. By severing the asymmetriesrelationship, the system may adapt to bandwidth requirements thatinherently vary throughout the system at various points in time.

It shall be further appreciated that the present invention does notrequires that hubs 105-108 begin or end their transmit modes or receivemodes at the exact times. However, more accurate synchronization reducesthe guard time and thereby maximizes the system throughput. Moreover,the present invention does not require any particular allocation ofchannel bandwidth to subs. It shall be appreciated that any number ofchannel division techniques may be utilized. All of the bandwidth duringa single transmit/receive cycle may be allocated to a particular sub.Alternatively, each sub in the sector may receive a designated portionof the available bandwidth per transmit/receive cycle in a TDM/TDMAscheme. Alternatively, the subs may be allocated bandwidth according toa polling scheme. The hubs may implement any number of algorithms toschedule bandwidth to particular sub units. The receive and transmitmodes may be divided through other techniques. For example, the subs mayemploy a CSMA/CD technique to send bursts to the hubs. Alternatively,the system may employ a contention period and a contention free periodfor sub access to the communication channel.

It shall be appreciated that numerous other signaling may occur betweenthe hubs and subs on the selected channel in conjunction with thepresent invention. For example, the hubs may transmit broadcast burstsintended for all sub units. The hubs may transmit control channelbursts. Additionally, the hubs may transmit a beacon signal containingtiming information or a network allocation vector to allow sub units tosynchronize with the hub. The signaling may include requests totransmit, permission to transmit, or acknowledgment of data bursts.

It shall be appreciated that present invention does not require rigiddefinition of the transmit and receive modes. For example, TDM/TDMAtelephony systems rigidly define the timing and duration of receive andtransmit modes to optimize the systems to carry voice traffic. Incontrast, the present invention may operate within a system that hasasymmetric transmit and receive modes. Also, the present invention maybe employed in a system that dynamically changes the duration of thetransmit and receive modes. Exemplary dynamic bandwidth allocationsystems and methods that may be employed in conjunction with the presentinvention are described in the above referenced patent application,entitled “SYSTEM AND METHOD FOR BROADBAND MILLIMETER WAVE DATACOMMUNICATION.” To facilitate dynamic variation of bandwidth allocatedto transmit and receive modes according to a preferred embodiment, hubspossessing synchronized sectors of the preferred embodiment communicatethe variations to corresponding hubs and/or a common control system.Accordingly, a further aspect of the present invention provides atelemetry communication channel for synchronizing transmit and receivemodes of hubs subject to co-channel coupling.

Several approaches may be taken to provide this communication channel.Leased connections from a ILEC (incumbent local exchange carrier) may beutilized for the synchronizing telemetry. However, it is preferred toutilize communication resources associated with the point to multipointsystem, rather than ILEC connections. Accordingly, sectorsynchronization telemetry may utilize a backhaul associated with thepoint to multipoint network. A backhaul may be implemented in any formof communication means, such as a broadband fiber-optic gateway or otherbroadband data grade connection, T1 communications lines, a cablecommunication system, or the like. However, a connection to the backhaulor other system connected to the backhaul is required for each hub of acluster that implements sector synchronization utilizing such a controlchannel. Although this may be sufficient in many systems, it is not anoptimal solution as particular systems may have hubs that are notconnected to the backhaul.

FIG. 5 illustrates a preferred option for synchronization telemetryinvolving a narrow carrier band adjacent to the primary carrier band. Ina preferred embodiment of the present invention, the spectrum of thepoint to multipoint system is divided into discrete 50 MHz channels. Theprimary data communication occurs via a Quadrature Amplitude Modulation(QAM) carrier 501 that occupies approximately 46 MHz. Additionally,narrow band adaptation carrier 502, preferably having a bandwidth of 130kHz, is established in the guard space of the 50 MHz channel to providethe synchronization telemetry. The hubs preferably utilize 2-level FSKmodulation to signal information via adaptation carrier 502. In apreferred embodiment, adaptation carrier 502 comprises a 100 kbpssignaling rate, 10 dB C/N for 10⁻¹² BER, 1/2 concatenated coding, andtransmit power 10 dB below the QAM power level. By utilizing this typeof channel, the control channel may be transmitted and/or received viathe adjacent sector antenna beams of a particular cluster of hubs.

It shall be appreciated that narrow band adaptation carrier 502 providesa preferred signaling channel optimized for the 50 MHz system. However,it shall be appreciated that the telemetry control channel is notrequired to be implemented as a narrow band carrier. If the presentinvention is utilized in a broadband point to multipoint system, thetelemetry control channel may be spread spectrum processed across alarger spectrum. Additionally, it is not required to located adaptationcarrier 502 in guard space associated within a predefined channel. Theadaptation carrier may be implemented utilizing distinctly allocatedspectrum.

In a preferred embodiment, adjacent hubs utilizing the present inventionmay receive bandwidth requests from their respective sub units. The hubsmay perform calculations based upon the bandwidth calculations. In thistype of a system, a bandwidth controller may be located in one hub toreceive the results of the bandwidth calculations via adaptation carrier502. Alternatively, the bandwidth controller may by implemented as aseparate system link to the respective hubs.

The bandwidth controller utilizes the received calculations to determineoptimal transmit and receive mode durations for synchronized sectors.The controller hub utilizes the adaptation carrier to signal thedetermined transmit and receive mode durations to the hubs. At thispoint, the hubs utilize the durations to allocate transmit and receiveresources to their respective subs within the adjacent sectors. It shallbe appreciated that the controller may receive the bandwidth requestsand perform the calculations directly. However, performing thecalculations at the hubs is preferred, since it distributes theprocessing requirements more efficiently. Also, it shall be appreciatedthat the hubs may contain logic to control receive and transmit modes inthe event that the adaptations carrier link is interrupted. For example,the hubs may temporarily revert to a predefined lengths for transmit andreceive modes. Alternatively, the hubs may temporarily define receiveand transmit modes of equal lengths.

For example, a bandwidth controller of the present invention may monitorthe instantaneous traffic demands on both forward and reverse links tothereby determine the appropriate amount of ATDD and/or asymmetry atwhich to operate the carrier channels. The bandwidth controller of thepreferred embodiment of the present invention is operable upon aprocessor (CPU) and associated memory (RAM) of a hub of the presentinvention. The controller may contain a record of adjacent antenna beamsand respective channels in a non-volatile memory in order to effect thedesired synchronization. Alternatively, the bandwidth controller mayoperate in an environment that dynamically varies sectors and/ordynamically assigns channel to various sectors. In this environment, thebandwidth controller may communicate with the portions of the systemthat effects the sector configuration and/or channel assignmentalgorithms to obtain information concerning adjacent antenna beams andtheir channels. Of course, additional and/or other apparatus, such as ageneral purpose processor based computer system having an appropriatealgorithm controlling operation thereof, may be utilized for operationof the bandwidth controller of the present invention.

With reference now to FIG. 6A, the set 600 is a notional depiction ofeight available frequency channels, also referred to herein as“frequencies”, for a communication system with two polarizationsavailable per frequency channel. The set 601 of frequencies are at onepolarization and the set 602 of frequencies is at another polarization.Preferably, the polarizations of the frequency set 601 and the frequencyset 602 are mutually orthogonal to minimize the possibility ofinterference between antennas operating at the same frequency butdifferent polarizations as discussed further below. The polarizationscan be, but are not limited to, horizontal and vertical alignments orslant left and slant right alignments.

It should be understood that although the discussion below developsfrequency re-use patterns for eight frequencies and two polarizations,the present inventive system and method is not limited to eightfrequencies and two polarizations. The principles on which the frequencyre-use patterns herein disclosed are applicable likewise apply insituations where more than eight frequencies are available for thecommunication system deploying a frequency reuse pattern of the presentinventive system and method.

FIG. 6B depicts eight cells, such as the cells illustrated in FIG. 2A,where each cell is divided into four 90° substantially non-overlappingsectors. The hub of each cell has at least one antenna per sector, forexample the hub 105 shown in FIG. 2B. As shown in FIG. 6B, opposingsectors of a cell operate with the same frequency/polarizationassignment. Taking cell 610 as an example, sectors 610A and 610D operateat frequency/polarization 601A while sectors 610B and 610C operate atfrequency/polarization 602T. Although the sector designations are onlyshown for the cell 610, is it to be understood that the sectordesignations apply to every cell and are used throughout thespecification and drawings. With eight frequencies and two polarizationsper frequency available as shown in FIG. 6A, there are 16 uniquefrequency/polarization sector assignments, or “degrees of freedom”,available. It is important for minimizing adjacent channel andco-channel interference in a frequency re-use plan to maximize the“distance” between the frequency/polarization sector assignments in acell, i.e., the largest frequency separation and orthogonal polarizationassignment is preferred. Additionally, for adaptive time division duplexsystems (“ATDD”) maximizing frequency separation minimizes couplingproblems associated with independent dynamic asymmetric frame usagewithin a cell. The pattern of assignment of the 16 degrees of freedom asshown in FIG. 6A is preferred since that pattern results in the maximum“distance” between sector assignments for a cell. The present inventivesystem and method contemplates the use of other patterns of assignmentof the 16 degrees of freedom.

Using the pattern of sector assignments discussed above, there are eightunique “cell types” available if each of the 16 sector assignments, ordegrees of freedom, is used once. Each of the cells in FIG. 6B is of aunique cell type. The eight cell types will be arranged in a particularmanner so as to minimize co-channel and adjacent channel interferencewhile obtaining maximum coverage of an operating area for acommunication system which has the frequency/polarization assignments ofFIG. 6A.

With attention now to FIG. 7, a section of a multi-cell frequency re-usepattern is depicted. As shown in the Figure, the 16-cell four-by-fourrectilinear grid 710 is comprised of the four two-by-two groups, 701through 704. The 16-cell grid 710 is repeatable vertically andhorizontally, referenced to the orientation of FIG. 7, so as to be ableto cover an area that is larger than the area covered by one instance ofthe grid 710. The cells in the grid 710 are arranged so that each celloccupies a unique rank and file position, where all the cells on thebottom row of FIG. 7 are in the rank designated 720 and where all thecells in the left-most column of FIG. 7 are in the file designated 730.The cells in the 16-cell rectilinear grid 710 are arranged so that rankand file adjacent cells are tangent but diagonally adjacent cells arenot tangent. The rank and file designations are arbitrary and are onlyused as a convenience to accurately describe the arrangement of cells inthe pattern. The rank and file designations are not part of theinvention and should not be construed as limiting the invention in anyway.

Referring now to FIG. 8, the 4-cell group 703, located in the lowerleft-hand quadrant of the rectilinear grid 710 in FIG. 7 is depicted.Each one of the four cells in the cell group 703 is a unique one of theeight cell types discussed above and shown in FIG. 6B. The cell 650 istangent to its rank and file adjacent cells, i.e., the cell 650 istangent to the cells 610 and 660. The cells 610, 620, 650, and 660 areoriented in the cell group 703 such that the polarization of facingcells for rank and file adjacent cells is not the same. For example, thesector 650B in the cell 650 is of one polarization while its facingsector in the rank adjacent cell 660, the sector 660A is of the otherpolarization (reference the two polarizations in FIG. 6A). By inspectionof FIG. 7 and FIG. 8, it is shown that for each of the four cell groups,701 through 704, the polarization of facing cells for rank and fileadjacent cells is not the same. This orientation of the cells within agroup works to minimize co-channel and adjacent channel interference asdiscussed above.

Referring back to FIG. 7, and with attention now to the cell group 704,each one of the four cells in the cell group 704 is a unique one of theeight cell types discussed above and shown in FIG. 6B. Additionally,each of the cells in the cell group 704 is of a different cell type fromthe cell types used in the cell group 703. In other words, of the eightcell types depicted in FIG. 6B, four of those cell types are used in thecell group 703 and the other four of those cell types are used in thecell group 704. The orientation of the cells in the cell group 704 issimilar to the orientation of the cells in the cell group 703 asdiscussed above: the polarization of facing cells for the rank and fileadjacent cells is not the same. Furthermore, and preferably, thepolarization of facing cells for the rank adjacent cells for the cells620, 660, 630, and 670 are different, as shown in FIG. 7.

Having discussed the orientation and arrangement of the cells in thefour cell groups, it should be noted that there is a relationshipbetween the cells in the cell groups 703 and 702 as well as arelationship between the cells in the cell groups 704 and 701. Referringto the cell groups 703 and 702 in FIG. 7, it can be seen that the samefour cell types appear in each of the cell groups and that thearrangement of the cells in each of the cell groups is the same, i.e.,the cell 650 in the cell group 703 is the same cell type as the cell650S in the cell group 702. However, the frequency/polarizationassignments for each cell have been swapped between the pairs ofopposing sectors. Whereas for the cell 650 in the cell group 703 theupper right and lower left sectors are of a first frequency/polarizationcombination, the same first frequency/polarization combination appearsin the upper left and lower right sectors of the cell 650S in the cellgroup 702. The same is true for each cell in groups 703 and 702. Anotherway to view the relationship is that the cells in the cell group 702have been rotated 90° from the orientation of the cells in the cellgroup 703. Likewise, the cells in the cell groups 704 and 701 arerelated in the same manner.

The reason for the change in orientation of the cells between cellgroups 703/702 and 704/701 is to minimize co-channel interferencebetween the sectors of the cells of the same cell type. If, forinstance, the cell 650S was of the same orientation as the cell 650, thefacing sectors 650A of the cell 650 and 650SC of the cell 650S would beoperating on the same frequency with the same polarization. If a cellradius is designated as “R”, the distance between the hubs of the cells650 and 650S is 4R√{square root over (2)}. This distance may beinsufficient to prevent co-channel interference. The swap offrequency/polarizations for the opposing sectors helps to overcome theproblem of insufficient distance between the hubs. Using the frequencyre-use plan of FIG. 7, the distance between hubs with facing sectorsoperating with the same frequency/polarization is 8R√{square root over(2)}, which is double the distance from the example above. The patterndescribed above for the four-by-four rectilinear grid 710 can berepeated horizontally and vertically in order to provide coverage for anarea larger than the grid 710. As shown in FIG. 7, a rank and file ofcells are repeated to illustrate the idea of horizontal and verticalrepeatability. It is to be understood that the present invention is notlimited to the specific number of cells shown in FIG. 7 nor to thespecific assignment of cells types or sector orientations. It iscontemplated that any repeatable rectilinear grid using the conceptsdescribed above are within the scope of the patent.

Turning now to FIG. 9, a different pattern of cells is depicted,referred to herein as the “shift and squish” pattern. As can be seenfrom FIG. 7, the repeatable pattern of the rectilinear grid 710 allowsfor a sizeable area of dead space between the cells. The shift andsquish pattern 910 eliminates much of that interstitial dead space. Aswith the rectilinear grid 710, the shift and squish pattern 910comprises 16 cells of two each of eight cell types. The lower two rowsof cells in the shift and squish pattern 910, similar to the lower tworanks of cells in the rectilinear grid pattern 710, are composed of oneeach of the eight cell types pattern 910 are composed of another set ofone each of the same eight cell types as the lower two rows, similar tothe upper two ranks of cells in the rectilinear grid pattern 710 beingcomposed of another set of one each of the same eight cell types as thelower two ranks. However, unlike the rectilinear grid 710, the upper torows of cells of the shift and squish pattern 910 are not arranged inthe same relative orientation as the lower two rows of cells within theshift and squish pattern 910. For example, the cells 901 through 904 arearranged in the order, from left to right, 901/902/903/904 while thecorresponding cells 901S through 904S are arranged, left to right,904S/901S/902S/903S. The same relationship holds for the cells in theother two rows of the grid 910. Additionally, the frequency/polarizationassignments of the two pairs of opposing sectors for the cells of acorresponding cell type are swapped.

The shift and squish pattern 910 is repeatable as shown in FIG. 9. The16 cells in the pattern are arranged so that no one cell is tangentiallyadjacent, in any direction, to two cells of the same cell type. Thisrelationship holds true as the pattern is repeated as shown in FIG. 9.

The spacing between hubs of cells having facing sectors operating withthe same frequency/polarization in the shift and squish pattern 910,such as cells 901 and 911, is approximately 10R, which is approximately88% of the distance between hubs with facing sectors operating with thesame frequency/polarization in the rectilinear grid 710. The distancebetween the hubs of cells 901 and 911 should be sufficient to preventco-channel interference.

With reference now to FIG. 10, a section of another multi-cell frequencyre-use pattern is depicted. The 16-cell four-by-four rectilinear grid1010 is comprised of the four two-by-two groups, 1001 through 1004. The16-cell grid 1010 is repeatable vertically and horizontally, referencedto the orientation of FIG. 10, so as to be able to cover an area that islarger than the area covered by one instance of the grid 1010. The cellsin the grid 1010, similar to the cells in the grid 710 of FIG. 7, arearranged so that each cell occupies a unique rank and file position andso that rank and file adjacent cells are tangent but diagonally adjacentcells are not tangent.

FIG. 11 A depicts the set 1100 of the eight available frequency channelsused for a communication system with two polarizations available perfrequency channel, similar to the set of frequencies 600 in FIG. 6A. Ofthe 16 frequency/polarization degrees of freedom in the set 1100, theset 1103 of eight frequency/polarization degrees of freedom and the set1104 of the eight other frequency/polarization degrees of freedom aredepicted. The set 1103 of degrees of freedom are used in the frequencyre-use pattern of FIG. 10. The set 1104 of degrees of freedom are notnecessary to populate the cells of the frequency reuse pattern of FIG.10 and are held in reserve for possible late use, as described below.

FIG. 11B shows eight cell types used in the frequency re-use patternrectilinear grid 1010 of FIG. 10. As shown in FIG. 11B, each sector of aparticular cell of each of the eight cell types operates with uniquefrequency/polarization assignment relative to the other sectors of thatcell. For each cell type, a pair of adjacent sectors operate with afirst polarization and the other pair of adjacent sectors operate with asecond polarization of the two available polarizations. Taking cell 1110as an example, each sector 1110A through 1110D operates at a differentfrequency/polarization each from the other. With four frequencies andtwo polarizations per frequency available as shown in FIG. 11A, thereare eight degrees of freedom available. With the limitations to bediscussed below, eight different cell types are used to populate therectilinear grid 1010.

Referring now to FIG. 12, the 4-cell group 1003, located in the lowerleft-hand quadrant of the rectilinear grid 1010 in FIG. 10 is depicted.Each one of the four cells in the cell group 1003 is a unique one of theeight cell types discussed above and shown in FIG. 11B. Additionally,facing sectors for each cell in the 4-cell group 1003 are of the samefrequency/polarization, regardless of whether the cell is rank and fileadjacent or diagonally adjacent. For example, as shown in FIG. 12, thecenter-facing sectors for all four cells, 1110D, 1120C, 1150B, and1160A, are all of the same frequency/polarization assignment.Additionally, the sector 1110C of the cell 1110 and the sector 1150A ofthe cell 1150 are facing and have the same frequency/polarizationassignment. The same holds for the following sectors: 1150D and 1160C,1160B and 1120D, and 1110B and 1120A. Furthermore, the opposing sectorsof the diagonally adjacent cells in the 4-cell group 1003 have the samefrequency/polarization assignment: the sectors 1150C and 1120B and thesectors 1110A and 1160D. These frequency/polarization assignments allowfor repeatability of the pattern of rectilinear grid 1010, as seen inFIG. 10, while minimizing co-channel and adjacent channel interference.

Referring back to FIG. 10, and with attention now to the cell group1004, each one of the four cells in the cell group 1004 is a unique oneof the eight cell types discussed above and shown in FIG. 11B.Additionally, each of the cells in the cell group 1004 is of a differentcell type from the cell types used in the cell group 1003. In otherwords, of the eight cell types depicted in FIG. 11B, four of those celltypes are used in the cell group 1003 and the other four of those celltypes are used in the cell group 1004. The orientation of the cells inthe cell group 1004 is similar to the orientation of the cells in thecell group 1003 as discussed above: facing sectors for each cell in the4-cell group 1004 are of the same frequency/polarization, regardless ofwhether the cell is rank and file adjacent or diagonally adjacent.

Having discussed the orientation and arrangement of the cells in thefour cell groups, it should be noted that there is a relationshipbetween the cells in the cell groups 1003 and 1002 as well as arelationship between the cells in the cell groups 1004 and 1001.Referring to the cell groups 1003 and 1002 in FIG. 10, it can be seenthat the same four cell types appear in each of the cell groups and thatthe arrangement of the cells and the orientation of the sectors withinthe cells in each of the cell groups is the same, i.e., the cell 1150 inthe cell group 1003 is the same cell type as the cell 1150 s in the cellgroup 1002. Likewise, the cells in the cell groups 1004 and 1001 arerelated in the same manner.

The rectilinear grid 1010 can be repeated horizontally and verticallysimilar to the repeatability of the rectilinear grid 710. Note that allof the inward-facing sectors of any two-by-two grid of four cells withinthe repeated pattern have the same frequency/polarization assignments.Such an arrangement allows for the synchronization of thoseinward-facing sectors as described more fully above.

The distance between any two facing sectors with the samefrequency/polarization assignment that are not adjacent facing sectorsis 6R√{square root over (2)}. This distance should be sufficient toprevent co-channel interference between the non-adjacent facing sectorswith the same frequency/polarization assignment. If there is co-channelinterference, the two groups of four cells that have the interferingnon-adjacent facing sectors can also be synchronized to avoid theco-channel problem.

With reference directed towards FIG. 13, a rectilinear grid 1310 isshown which is similar to the rectilinear grid 1010 of FIG. 10. However,the grid 1310 includes sector overlays for those sectors, hereinreferred to as incumbent sectors, for which the capacity of the systemis insufficient to support the user demands in those sectors. The addedsector overlays are indicative of an added antenna and correspondingcircuitry at the hub of the cell in which the overlay lies, as is knownin the art. The added sector overlay typically is not a simplereplacement for the incumbent sector. The added overlay operates at adifferent frequency than the incumbent sector but with the samepolarization. This configuration allows for the sharing of protection,or redundant, equipment between the incumbent and overlay sectors. Thesize of the overlay sectors is typically equal to or less than the sizeof the incumbent sector. As shown in FIG. 13, the overlay sectors are45° sectors, but the present inventive system and method is not limitedto 45° sectors. Additionally, FIG. 13 shows the overlay sectors 1390added to one of each of the sectors of the four cells 1 through 4, whichis merely an exemplary use of overlay sectors. The present inventivesystem and method is not limited to adding an overlay sector to groupsof four facing sectors and it contemplates adding fewer or more overlaysectors as required by user demand. Adding overlay sectors to each offour facing sectors of four adjacent cells enables the four addedoverlay sectors to be synchronized in a manner similar to thesynchronization of the underlying four incumbent sectors. Naturally,less than four overlay sectors can be added and synchronized as well.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the invention as defined by the appended claims. Moreover, thescope of the present application is not intended to be limited to theparticular embodiments of the process, machine, manufacture, compositionof matter, means, methods and steps described in the specification. Asone of ordinary skill in the art will readily appreciate from thedisclosure of the present invention, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein may be utilized according to the present invention.Accordingly, the appended claims are intended to include within theirscope such processes, machines, manufacture, compositions of matter,means, methods, or steps.

1. A repeatable pattern of frequency reuse in a wireless communicationsystem comprising: sixteen substantially circular cells of approximatelythe same radius arranged in a four-by-four grid such that no two cellssubstantially overlap and where each cell is substantially tangent withits adjacent rank and file neighbors, wherein each cell includes a hubwith four antennas wherein each antenna services a separate one of foursubstantially non-overlapping ninety degree sectors and is capable ofcommunicating on each of eight frequencies and on either of twopolarizations per frequency, whereby for each hub one set of opposingninety degree sectors communicate on a one of said eight frequencies ata one of said polarizations and the other set of opposing ninety degreesectors communicate on a different one of said eight frequencies at theother of said polarizations; eight cell types wherein each cell typecommunicates over a unique combination of frequencies; a first and asecond group of four cells, each group comprising a two-by-two grid ofcells such that, said first group of four cells comprising fourdifferent cell types of said eight cell types, said cells arranged sothat facing sectors of rank and file adjacent cells are of a differentpolarity, and said second group of four cells comprising the remainingfour different cell types, said cells arranged so that facing sectors ofrank and file adjacent cells are of a different polarity; a third and afourth group of four cells, each group comprising a two-by-two grid ofcells such that, said third group of four cells comprising the same fourcell types as said first group wherein the frequency and polarizationassignments are interchanged between the pairs of opposing sectors foreach cell, said four cells arranged identically to the cells in saidfirst group, and said fourth group of four cells comprising the samefour cell types as said second group wherein the frequency andpolarization assignments are interchanged between the pairs of opposingsectors for each cell, said four cells arranged identically to the cellsin said second group; wherein said four groups of cells are arranged insaid four-by-four grid so that said first and third group of cells arenot rank and file adjacent and so that facing cells between rank andfile adjacent groups are of different frequencies.
 2. The pattern ofclaim 1 wherein said polarizations are mutually orthogonal.
 3. Thepattern of claim 1 wherein the communication system is a time divisionduplex system.
 4. The pattern of claim 3 wherein the communicationsystem is an adaptive time division duplex system.
 5. The pattern ofclaim 4 wherein said eight frequencies are in the millimeter frequencyrange.
 6. The pattern of claim 5 wherein said eight frequencies are eachin the range of 10-60 GHz.
 7. The pattern of claim 1 wherein the cellsare not synchronized.
 8. The pattern of claim 7 wherein the sectorswithin the cells are not synchronized.
 9. The pattern of claim 1 whereinsaid sixteen cells are generally circular, are of approximately the sameradius, and are arranged in a four-by-four square grid such that thedistance between the centers of any two horizontally and any twovertically adjacent cells is approximately twice a cell radius.
 10. In apattern of sixteen cells arranged in a four-by-four grid in a multi-cellpattern of cells forming a rectilinear grid in a communication systemwherein each cell is divided into four ninety degree sectors with atleast one antenna per sector whereby each antenna is capable ofoperating in one of two polarization modes for each of eightcommunication frequencies whereby for each hub one set of opposingninety degree sectors communicate on a one of said eight frequencies ata one polarization and the other set of opposing ninety degree sectorscommunicate on a different one of said eight frequencies at the otherpolarization, the method of reducing co-channel interference comprisingthe steps of: (a) dividing the sixteen cells into four groups of fourcells whereby each group comprises a two-by-two grid of cells; (b)providing eight cell types wherein each cell type communicates over aunique combination of polarization modes and frequencies; (c) providinga first group of four cells comprising four different cell types of saideight cell types, said cells arranged so that facing sectors of rank andfile adjacent cells are of a different polarity; (d) providing a secondgroup of four cells comprising the remaining four different cell types,said cells arranged so that facing sectors of rank and file adjacentcells are of a different polarity; (e) repeating said first and secondgroup of cells diagonally within said sixteen cell pattern; (f) rotatingthe frequency and polarization assignments in the sectors of each cellof the repeated first and second group of cells by ninety degreesrelative to the frequency and polarization assignments in the sectors ofthe first and second group of cells.
 11. The method of claim 10 whereinadjacent channel interference is reduced.
 12. The pattern of claim 10wherein said polarizations are mutually orthogonal.
 13. The pattern ofclaim 12 wherein the communication system is a time division/duplexsystem.
 14. The pattern of claim 13 wherein the communication system isan adaptive time division duplex system.
 15. The pattern of claim 14wherein said eight frequencies are in the millimeter frequency range.16. The pattern of claim 15 wherein said eight frequencies are each inthe range of 10-60 GHz.
 17. A pattern of frequency reuse in a wirelesscommunication system including sixteen substantially circular cells ofapproximately the same radius arranged in a repeatable four-by-four gridforming a parallelogram so that the edge of any one cell is tangent tothe edge of six other cells, wherein each cell includes a hub with fourantennas wherein each antenna services a separate one of foursubstantially non-overlapping ninety degree sectors and is capable ofcommunicating on each of eight frequencies and on either of twopolarizations per frequency, whereby for each hub one set of opposingninety degree sectors communicate on a one of said eight frequencies ata one polarization and the other set of opposing ninety degree sectorscommunicate on a different one of said eight frequencies at the otherpolarization, said pattern comprising: eight cell types wherein eachcell type communicates over a unique combination of frequencies; a firstgroup of four cells comprising four different cell types of said eightcell types, said cells arranged so that the centers of each cell arecollinear and the edges of adjacent cells are tangent, whereby facingsectors of adjacent cells are of a different polarity; a second group offour cells comprising the remaining four different cell types, saidcells arranged so that the centers of each cell are collinear and theedges of adjacent cells are tangent, whereby facing sectors of adjacentcells are of a different polarity, and whereby said first and secondgroups of cells are arranged so that each cell of each group is adjacentto and tangent to at least one cell of the other group of cells; a thirdgroup of four cells comprising the same four cell types as said firstgroup wherein the frequency and polarization assignments are exchangedbetween the pairs of opposing sectors for each cell, said four cellsarranged so that the centers of each cell are collinear and the edges ofadjacent cells are tangent, and whereby said second and third groups ofcells are arranged so that each cell of each group is adjacent to andtangent to at least one cell of the other group, and whereby no celladjacent to a cell in the third group is also adjacent to a cell in thefirst group with a corresponding combination of frequencies as said cellin the third group; a fourth group of four cells comprising the samefour cell types as said second group wherein the frequency andpolarization assignments are exchanged between the pairs of opposingsectors for each cell, said four cells arranged so that the centers ofeach cell are collinear and the edges of adjacent cells are tangent, andwhereby said third and fourth groups of cells are arranged so that eachcell of each group is adjacent to and tangent to at least one cell ofthe other group, and whereby no cell adjacent to a cell in the fourthgroup is also adjacent to a cell in the second group with acorresponding combination of frequencies as said cell in the fourthgroup.
 18. The pattern of claim 17 wherein said sixteen cells aregenerally hexagonal in shape.
 19. The pattern of claim 17 wherein saidpattern is repeated horizontally and vertically.
 20. The pattern ofclaim 17 wherein said polarizations are mutually orthogonal.
 21. Thepattern of claim 20 wherein the communication system is a time divisionduplex system.
 22. The pattern of claim 21 wherein the communicationsystem is an adaptive time division duplex system.
 23. The pattern ofclaim 22 wherein said eight frequencies are in the millimeter frequencyrange.
 24. The pattern of claim 23 wherein said eight frequencies areeach in the range of 10-60 GHz.
 25. The pattern of claim 24 wherein thecells are not synchronized.
 26. The pattern of claim 25 wherein thesectors within the cells are not synchronized.
 27. A pattern offrequency reuse in a wireless communication system including sixteencells arranged in a four-by-four grid including four sub-clustersarranged in a two-by-two grid of four cells, wherein each cell includesa hub with four antennas in which each antenna services a separate oneof four substantially non-overlapping ninety degree sectors and iscapable of communicating on each of eight frequencies and on either oftwo polarizations per frequency, wherein for each hub each sectorcommunicates on a different frequency in which two adjacent sectorscommunicate at a one polarization and the other two adjacent sectorscommunicate at the other polarization, said pattern comprising: eightcell types wherein each cell type communicates over a unique combinationof frequencies whereby the eight cell types are comprised of fourfrequencies at said one polarity and four frequencies at said otherpolarity; a first sub-cluster comprising four different cell types ofsaid eight cell types, said cells arranged so that facing sectors ofadjacent cells communicate on a same frequency and a same polarization;a second sub-cluster comprising the remaining four different cell types,said cells arranged so that facing sectors of adjacent cells communicateon a same frequency and a same polarization; a third sub-clusteridentical to said first sub-cluster; a fourth sub-cluster identical tosaid second sub-cluster; wherein said sub-clusters are arranged in saidfour-by-four grid so that said first and third sub-clusters are notadjacent and so that said facing cells between adjacent sub-clusterscommunicate on a same frequency and a same polarization.
 28. The patternof claim 27 wherein said polarizations are mutually orthogonal.
 29. Thepattern of claim 27 wherein the communication system is a time divisionduplex system.
 30. The pattern of claim 29 wherein the communicationsystem is an adaptive time division duplex system.
 31. The pattern ofclaim 30 wherein said eight frequencies are in the millimeter frequencyrange.
 32. The pattern of claim 31 wherein said eight frequencies areeach in the range of 10-60 GHz.
 33. The pattern of claim 32 wherein onesof said cells are synchronized.
 34. The pattern of claim 33 whereinadjacent sectors communicating on a same frequency and a samepolarization are synchronized.
 35. The pattern of claim 34 wherein saidadjacent sectors communicate with a common dynamic asymmetricsynchronization.
 36. The pattern of claim 27 including at least oneadditional sector communicating on a frequency and polarizationcombination of said eight frequencies and two polarizations that is notused in said pattern, whereby said additional sector is overlayed on atleast one of the sectors in said pattern that has a similar polarizationto the polarization of said additional sector.
 37. The pattern of claim36 wherein said additional sector is a ninety-degree sector.
 38. Thepattern of claim 36 wherein said additional sector is a forty-fivedegree sector.
 39. A method of reducing co-channel interference in ahorizontally and vertically repeatable pattern of cells in a multi-cellpattern of cells forming a rectilinear grid in a communication systemwherein each cell includes a hub with four antennas wherein each antennaservices a separate one of four substantially non-overlapping ninetydegree sectors and is capable of communicating in one of twopolarization modes for each communication frequency used by thecommunication system, whereby for each hub one set of opposing ninetydegree sectors communicate on a one of said communication frequencies ata one of said polarizations and the other set of opposing ninety degreesectors communicate on a different one of said communication frequenciesat the other of said polarizations, the method comprising the steps of:(a) providing eight cell types wherein each cell type comprises a uniquecombination of said two sets of frequency and polarization; (b)providing two sub-clusters of cells each of four cells arranged in atwo-by-two grid wherein a first sub-cluster comprises four cells each ofa different cell type of said eight cell types and wherein a secondsub-cluster comprises four cells each of a different cell type of theremaining four cell types; (c) alternating said two sub-clustershorizontally and vertically within the multi-cell pattern of cells; and(d) orienting each pair of alternate diagonal cells within themulti-cell pattern of cells ninety degrees relative to each other. 40.The method of claim 39 wherein adjacent channel interference is reduced.41. The pattern of claim 39 wherein said polarizations are mutuallyorthogonal.
 42. The method of claim 41 wherein the number of frequenciesis eight.
 43. The method of claim 41 wherein the number of frequenciesis at least eight.
 44. The method of claim 43 wherein each cell type isrepeated once within the pattern.
 45. The pattern of claim 41 whereinthe communication system is a time division duplex system.
 46. Thepattern of claim 45 wherein the communication system is an adaptive timedivision duplex system.
 47. The pattern of claim 46 wherein said eightfrequencies are in the millimeter frequency range.
 48. The pattern ofclaim 47 wherein said eight frequencies are each in the range of 10-60GHz.